Apparatus for automatic nailing of preassembled wood stairs

ABSTRACT

Precut and grooved stringers, precut treads and risers are temporarily secured together in the form of a stair which is then received by an apparatus which automatically indexes the stair step by step past left, right and top banks of nailers which nail the stringers and risers to the treads to produce a permanently secured stair.

United States Patent 1 Ingram [54] APPARATUS FOR AUTOMATIC NAILING OF PREASSEMBLED WOOD STAIRS [76] Inventor: Harry T. Ingram, I800 Rankin Street, Raleigh, NC. 27604 [22] Filed: Dec. 29, 1971 21 Appl. No.: 213,310

[52] U.S. Cl. ..227/5, 227/44, 227/100 [51] Int. Cl. ..B27f 7/06 [58] Field of Search ..227/5, 7, 44, 45,

{56] References Cited UNITED STATES PATENTS Good et al ..227/99 51 May 15, 1973 3,443,303 5/l969 Groat ..227/44 X 3,591,067 7/l97l Vial ..227/100 X 3,637,126 l/l972 Heterick, Jr ..22 7/100 X Primary Examiner-Granville Y. Custer, Jr. Attorney- B. B. Olive [57] ABSTRACT Precut and grooved stringers, precut treads and risers are temporarily secured together in the form of a stair which is then received by an apparatus which automatically indexes the stair step by step past left, right and top banks of nailers which nail the stringers and risers to the treads to produce a permanently secured stair.

12 Claims, 16 Drawing Figures PATENTED I L973 SHEET 1 BF 6 INVENTOR m OE SHEET 2 or 6 1 lwmm Cm wwm I. nEDw In KP PATENIED MAY 1 51575 Jo zou I .3 i

INVENTQR HARRY T INGRAM ATTORNEY PATENTEU 9 733,020

SHEET u 0F 6 INVENTOR BY HARRY T INGRQM ATTORNEY PATENI am 51915 SHEET 8 BF 6 INVENTOR HARRY I INGRAM ATTORNEY APPARATUS FOR AUTOMATIC NAILING OF PREASSEMBLED WOOD STAIRS BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to machines for automatically nailing or stapling of wood components for the manufacture of prefabricated building units and particularly to machines for nailing assembled precut stringers, risers and treads intended to be prefabricated into a stair.

2. Description of the Prior Art It has been the practice in the building industry to lay out and saw stringers, risers and treads on the job when required for a wood stair. The components are then assembled and nailed together in place on the job. An improved practice has been to prefabricate the wood stair off the job and then transport the prefabricated stair to the job as a unit for installation. However, in this practice the stringers, risers and treads after being assembled and temporarily clamped are nailed together by use of a hand hammer and nails or by nailing with pneumatic nailers one nail at a time. Time is lost in aligning the nails with the respective risers and treads, in driving the nails and in moving from step to step to complete the nailing. The use of pneumatic nailers by individual operators also introduces various safety hazards. With the advent of nailing and stapling machines, referred to here collectively as nailers, various machines have been devised to make use of nailers for fastening wood components together into prefabricated building units. See, for example, US. Pat. No. 3,381,870. What the art has not provided has been an apparatus for temporarily assembling and clamping risers, treads and stringers together in the form of a prefabricated stair and for indexing the stair step by step past adjustably positionable banks of nailers which operate in synchronism with the indexing and which automatically nails the components together step by step.

SUMMARY OF THE INVENTION The risers, treads and stringers are first assembled and temporarily wedged and glued together on a worktable according to prior art procedures. At this stage the stringers arrive at the worktable precut to length, width and shape and after having gone through a double stair trenching machine which provides mating tread and riser grooves on one side surface to receive the risers and treads. The risers and treads arrive cut to size and with the treads prebored for bannister posts as might be later required. The stringers are placed parallel on the worktable and the risers and treads are then positioned and wedged in their respective riser and tread grooves by small wooden wedges which are driven in manually to help secure the components together. A quick drying glue is applied at selected junctures of the risers, treads and stringers. Small blocks are also glued in at selected junctures to give added stability to the finished stair. The assembled components during the wedging and after application of the glue are temporarily clamped together. After being wedged and glued together in this manner the components are unclamped and are then sufficiently secure to enable the stair to be moved as a unit to the next nailing operation with which the invention is primarily concerned.

The stair stringers are guided from the assembly worktable guide rails onto the nailing apparatus guide rails. Then the leading edge of the leading tread is engaged with a piston operated pusher or indexing device whose purpose is to automatically index the stair step by step past respective left, right and top banks of nailers. The nailing apparatus is energized by the left and right stringers actuating respective right and left electric and pneumatic control switches in the path of the stair and a series of automatic and cam switch operated control operations now commence to take place. In the first instance the pusher device engages the leading tread and pushes the stair forward to a first nailing position. The pusher is stopped and machine controls cause a piston operated stop member to be brought against the stair in opposition to the pusher so as to grip the stair between the pusher and stop member. That is, the pusher pushes on an underside surface and the stop member pushes in opposition on an outside surface. The machine control alsocauses the oppositely disposed right and left nailers to move in from the sides of the stair and to automatically drive a plurality of laterally aligned nails in through the sides of the stringers into the particular tread. At the same time a separate bank of top nailers are automatically actuated and move in to drive a plurality of laterally aligned nails which secure the respective tread and riser together. The nailers after completing their respective nailing operations are caused to automatically retract away from the stair. The stop member also retracts as do the top nailers. The pusher device now takes over, retracts, engages the next successive leading tread edge and pushes the stair forward until the next tread and riser set is properly positioned for nailing. At this time the stop member and the various left, right and top nailers are again activated to repeat the nailing sequence of the stringers to the tread as just explained. At the completion of this last sequence the stair is again indexed and the sequence repeats until the stringers are nailed to all of the sets of treads. Thenow nailed together stair is next moved from the nailing machine to another worktable for further finishing operations not associated with the invention.

From the foregoing it can be seen that once the stair components are temporarily wedged together, the stair can then be moved as an assembly and be engaged with the pusher and from then on until completion of the nailing the nailing operation is completely automatic. The mentioned left, right and top banks of nailers can be adjustable positioned to accommodate to various stair widths and pitches as can the pusher and stop mechanisms. Thus, with relatively minor and quick ad-- justments the apparatus of the invention can be changed from handling one size stair to another. Furthermore, various safety arrangements are built into the system to insure that the nailers operate only in the presence of material into which to nail.

DESCRIPTION OF THE DRAWINGS FIG. 1 is an exploded somewhat diagramatic view of the stair components which are assembled in the assembly operation which precedes the nailing operation.

FIG. 2 is a schematic electrical and pneumatic control diagram for the nailing apparatus, a heavy line indicating electrical and light lines pneumatic lines.

FIG. 3 is a rear elevation view of the nailing apparatus to show the general arrangement of the nailers, pusher and stop mechanism with the main cam control, conventional air lines and valves being left off for clarity.

FIG. 4 is a front elevation view of the nailing apparatus showing the same general arrangement but in this instance showing the motor driven cam control.

FIG. 5 is a right side elevation view of the nailing apparatus and partially showing the adjoining assembly and receiving tables.

FIG. 6 is a left side elevation view of the nailing apparatus and partially showing the adjoining assembly and receiving tables.

FIG. 7 is a partial perspective view of a typical pivotal mount for a side nailer bank.

FIG. 8 is a partial top view of the typical side nailer bank mount.

FIG. 9 is a partial left side view of the pusher mechanism.

FIG. 10 is an enlarged partial view of thepivotal pusher arm.

FIG. 11 is a partial top view of the basic frame of the nailing apparatus and showing the pusher mechanism and the laterally adjustable rails which support the stair during nailing.

FIG. 12 is a side view of the stair stop cylinder mechanism.

FIG. 13 is a fragmentary side view of the controls at the operators control station.

FIG. 14 is a perspective view illustrating the manner of adjustably and rotatably supporting the top nailers and stop mechanism and their operating cylinders.

FIG. 15 is a fragmentary side view of a stringer showing a typical array of nails connecting a stringer to a tread.

FIG. 16 is a fragmentary perspective view of a tread and riser showing a typical array of nails connecting the riser to the tread.

DESCRIPTION OF THE PREFERRED I EMBODIMENT Prior to describing the automatic nailing apparatus to which the invention is principally directed a description will be given of the assembly operation which precedes the nailing operation. In this regard it may be noted that a wood stair basically consists of a pair of grooved stringers 30, a suitable number of treads 31 and risers 32 as shown in FIG. I. These are initially assembled together on a worktable 35, FIGS. 5 and 6, by inserting the treads 31 and risers 32 in the appropriate tread and riser grooves 36 provided in the stringers 30 by a double stair trenching machine. That is, the stringers 30 are grooved by a double stair trenching machine prior to reaching the assembly table. After the respective treads 31 and risers 32 are installed in the stringers 30 the workmen drive wooden wedges 43 in adjacent the ends of the treads 31 and this tends to hold the assembly together as an assembled stair. As previously mentioned, it is also the practice to apply quick drying glue to the ends of the treads 31 and risers 32 to assist in securing the assembly together pending the nailing operation and during the setting of the glue the various components will be clamped together. Small strengthening blocks 33 are also often glued in at this stage as indicated.

During the assembly operation just explained it may be said that such operation starts with the treads 31, risers 32 and stringers 30 all cut to shape and size and with the stringers 30 grooved to receive the treads 31 and risers 32. Also, at the assembly table 35 the workmen will have available a supply of the mentioned wedges 43 and glue. During assembly the respective treads 31 and risers 32 receive an application of glue on their ends and are quickly dropped into their respective grooves 36. The assembly is clamped by pressure applied with wood clamps to the sides of the stringers 30 andthen the wedges 43 are driven in between the stringer grooves 30 and treads 31. While the stair assembly is now secured together sufficient for the next nailing operation it is of course not yet adequately fastened together to serve as a permanent stair. According to prior art practice as previously mentioned the assembled stair at this stage would be manually nailed together and much time would be lost in drawing aligning marks, in aligning the nails with the angle of the treads, in driving the nails in and in moving from tread to tread to complete the nailing of all the treads. The description now proceeds to the nailing operation and the nailing apparatus to which the invention is primarily directed from which it can be seen how this operation has been made into a uniform, safe and quick machine operation.

In the' drawings the various air and electric lines and framing used only to support or guide air lines have not been shown so as to better illustrate those features which are believed to be novel in the art. The nailing apparatus next to be explained includes a pusher or indexing apparatus, generally designated P, whose purpose is to index the stair step by step through the nailing apparatus. That is, the operator manually engages the first tread with the pusher apparatus P and the nailing apparatus then automatically takes over and indexes the stair step by step as each nailing operation takes place. Looking towards the machine in the same direction in which the stair is indexed, as in FIG. 4, there is a left bank of nailers, generally designated N-l, opposite a right bank of nailers, generally designated N-2. As each step comes into the appropriate indexed position, nailers N-l and N2 move in from opposite sides and drive nails through the stringers 30 into the particular positioned tread. At the same time a stop mechanism, generally designated S, moves down and engages the stair in opposition to the pusher P so that the stair is held steady during the nailing operation. Further, at this same time a bank of top nailers, generally designated N-3, moves in and nails the tread to the riser. Then the nailers N-l, N-2 and N-3 and the stop S move away and clear the stair for its next indexing step which is accomplished by the pusher P retracting, engaging the next rearward tread and pushing the stair forward by one step. Various pneumatic and electric controls are employed and are basically controlled by motor driven set of cams and cam operated valves, generally designated C in FIG. 4. The nailers N-l, N-2 and N-3, the pusher P and the stop S are operated by double acting pneumatic cylinders controlled by control C and other electric and pneumatic safety switches to be explained. Various adjustments are provided to accommodate to different size stairs and these will be dealt with as the description proceeds.

The description will next turn to a more detailed description of the adjustable frame which supports the stair during nailing. A left rail member 50 mounts a pair of blocks 51, 52, FIG. 11, which are slidably mounted on a pair of fixed rods 53, 54. Similarly, a right rail member 55 mounts a pair of blocks 56, 57 which are slidably mounted on the same set of fixed rods 53, 54. Rail members 50, 55 also mount respective pairs of threaded blocks 58, 59 and 60, 61 which receive a pair of threaded screw rod members 62, 63. A chain 70 is driven through sprockets 65, FIG. 5, and 66, FIG. 11, by a handle 71 which rotates rod 62. A chain 72 drives rod 63 from rod 62 through sprockets 67, 68, FIG. 11. Thus, in order to vary the width of stair accommodated by the machine the operator turns the handle 71 which rotates the first threaded rod member 62 which rotates the second threaded rod member 63 thus causing the two support rails 50, 55 to move in and out. In order to assist in the measurement of the spacing a tape rule 73 is secured to the frame as indicated. The basic frame includes the usual leg, front and side connecting members as shown in the drawings and which are not deemed necessary to discuss in detail.

It has been found necessary to reposition the banks of side nailing guns N-l, N-2 laterally each time a substantially narrower or wider stair than the one before is nailed in the machine and for this purpose the invention provides for the right and left nail gun banks N-l, NZ to be supported from rails 50, 55 and to be moved in and out with the respective left and right support rails 50, 55. In particular, asbest shown in FIGS. 3, 4 and 11, a right support frame arrangement having structural members 74, 75, 76, 77 and 78 forms an integral structure and is secured to the right rail member 55. A similar integral frame having structural members 84, 85, 86, 87 and 88 is secured to the left rail member 50. Thus, as the respective rail members 50, 55 are moved in and out to adjust for stair width these support frames are also moved in and out and thereby automatically adjust the banks of nailing guns N-l, N-2 accordingly. It will of course be understood that where a large quantity of the same or essentially the same size stair are being nailed together that rails 50, 55 and consequently the nailing gun banks N-l, N-2 are held fixed in some position appropriate to that width stair and from which the guns move in and out during nailing as later explained.

The description next describes the general construction and operation of the right nailer bank N-2 and from this will be understood the operation of the left nailer bank N-l. Remembering that the purpose of the right and left nailer banks N-l and N-2 is to install a plurality of laterally aligned nails through each stringer and into the respective tread and that the dimensions of stairs may vary, each nailer bank is adjustably positionable in various directions as shown. As shown in FIGS. 3, 4, 5, 6, 7, and 8, a mounting base 100 is secured to the frame plate member 78 which in turn is supported from members 75, 76, FIG. 11. Base 100 receives a shaft 102 which can be rotated in base 100 and clamped in a particular position by loosening and tightening lever 103 in a conventional split sleeve arrangement as best seen in FIGS. 7 and 8. An auxiliary sleeve mount 105 is suitably positioned and rigidly secured to shaft 102. Mount 105 in turn supports a double acting pneumatic cylinder 110 having an extensible rod 111 secured to an arm 112 which in turn is secured to a hub I13 slidably mounted on shaft 102. That is, whenever cylinder 110 is energized to move rod 111 out hub 113 moves out and when energized to move rod 111 in hub 113 moves in. A similar cylinder 109 acts through a similar arrangement to move the left nailers 132, 133, 134 in bank N-l. A pair of guide sleeves 115, 116, FIG. 8, slidably receive guide shafts 117, 118 whose ends are respectively rigidly secured in sleeves 119, 120 appended to hub mount 105. Thus, as hub 113 is moved in and out its rotative and axial positions are maintained by shafts 117, 118.

While the number of nailers in each bank is to some degree a matter of choice three nailers are used in each of the banks N-l and N-2 and four nailers in the bank N-3. Referring back specifically to the right nailer bank N-2 it can be seen that the nailers are mounted on a common support bar such that when shaft 102 is rotated and locked in a particular position by lever 103 all of the nailers 135, 136 and 137 in bank N-2 are properly aligned for driving a later-ally aligned group of nails. The nailers may vary as to specific type. A Magnum, Model 91900 F-Nailer made by the Paslode Company Division of the Signode Corporation, 8080 McCormick Boulevard, Skokie, Illinois 60076, is given as an example. This type of nailer receives an air supply through one line which effectively energizes the gun and through a second line receives a burst of control air at an appropriate time which tires the gun. The line providing the control air also serves as an exhaust line after each firing and appropriate relief valves, not shown, are provided for this purpose. Since this nailing operation, per se, is well-known the required air supply, control and exhaust lines are not identified or shown in detail. The control arrangement C for timing the required air supplies will, however, be later described.

In general, it can be said that the control mechanism C, later explained, in conjunction with an electric safety switch 140 and an air safety valve 141 controls the operation of the nailers N1, N-2, N-3, the stop mechanism S and the pusher mechanism P. Nailers NJ and N-2 are constructed and operate in the same manner. Thus, as to right nailer bank lN-2, control C regulates supply air to cylinder 110 which pushes nailers 135, 136 and 137 out. Control C also regulates supply air to each of the nailers and allows the supply air to be followed by a burst of control air to each of the nailers 135, 136, 137 which causes a nailing operation. Then, the nailer supply air is cut off and air is supplied to the opposite side of cylinder 110 to cause it to retract nailers 135, 136 and 137. On each nailing operation it will be understood that three nails are driven in on each side of the stair, three by bank N l and three by bank N-2, through the stringers and into the respective tread being secured. At the same time four nails are driven in through the respective riser, by the top bank N-3, and into the same respective tread. A description of the top nailer bank N3 is next given.

The top nailer bank N-3 is constructed and operates basically the same as the right and left nailer banks N-2 and N-3. In this regard it should be noted that the top nailers 150, 151, 152 and 153 constituting the top nailer bank N-3 can be positioned rotatively, laterally and forwardly for the particular size stair being nailed. Also, the stop mechanism S can be positioned forwardly and rotatively for the particular size stair. For this purpose the entire frame assembly for the top nailer bank N-3 and the stop mechanism S is pivoted on stub shafts 156, 157, FIG. 14, which are mounted in split sleeve supports which are loosened and tightened by the respective handles 158, 159. It will also be noted that the mentioned stub shafts are supported on the respective side plate members 160, 161. Referring specifically to plate 161 it will be noted that plate 161 is slidably mounted on bars 162, 163 and also mounts threaded mounts 165, 166 which receive a threaded bar 164 having a handle 167. Thus, by turning handle 167 plate 161 is moved forwardly and backwardly which in turn moves the entire right side of the top nailer bank N-3 and stop mechanism S forwardly or backwardly according to the direction of turning handle 167. It can also be seen without repeating the same detail construction that plate 160 is similarly mounted and that the left side of the supporting frame is adjusted forwardly and backwardly by rotating handle 168.

To continue with a more detailed description of the supporting frame shown in FIG. 14, stub shafts 156, 157 are integrally secured to and rotate with respective double acting cylinders 175, 176. A U-shaped frame member 172 is also mounted to be secured to and rotate with shafts 156, 157. Blocks 170 provide split tightening sleeves for supporting and securing shafts 156, 157 and are secured respectively to plates 160, 161. Cylinder 175 has a rod 177 and cylinder 176 has a rod 178 and which are respectively moved in and out according to the cylinder direction of movement. Rod 177 is secured to a U-shaped member 181 and rod 178 is secured to a similar U-shaped member 180. Members 180 and 181 in turn are joined by and support the nailer support bar 155, the stringer 185 and the stiffening arms 186, 187. Cylinder 176 mounts a hollow hub 190 which slidably receives a guide shaft 191 secured to member 180. Similarly, cylinder 175 mounts a hollow hub 193 which slidably receives a guide shaft 194 secured to member 181. In operation it can be seen that when cylinder rods 177, 178 are retracted nailer support bar 155 is moved in the down direction in FIG. 14 for a nailing operation and when cylinder rods 177, 178 are extended, support bar 155 is moved in the up direction in FIG. 14 which makes the nailers 150-153 inoperative.

Referring next to the stop mechanism S which is mounted on the same frame as the top nailer bank N-3, a stanchion 200 is secured to member 172 and mounts a downwardly sloped base plate 201. A double acting cylinder 203 is mounted on plate 201 and has a cylinder rod 204 which can be extended and retracted. Cylinder rod 204 is in turn connected through a sleeve 205 with a threaded guide rod 206 having an adjusting nut 207. Guide rod 206 has a smooth end portion 210 mounted in a hollow guide sleeve 208 fixed to plate 201. End portion 210 in operation is engaged with the stair as later explained and effectively prevents forward motion of the stair during the nailing operation. The exact amount which end portion 210 is allowed to move forward when cylinder 203 is actuated to extend its rod 204 is controlled by the position of adjusting nut 207 which strikes fixed sleeve 208 during forward travel. The general forward position of plate 201 on which the stop mechanism S is mounted is controlled by the previously mentioned levers 167, 168. That is, when levers I67, 168 are adjusted to adjust the forward position of the top nailer bank N-3 this also adjusts the forward position of the stop mechanism S.

The mentioned pusher mechanism P is best seen in FIGS. 6, 9, and 11. A pusher block 250 is shaped to engage the respective treads in turn and is mounted on a support member 251 having a pivotal mount on shaft 252 mounted on stanchions 253, 254 which in turn mount on plate 255. A spring 258 is suitably attached to keep the block 250 in the raised position shown in FIG. 10. Pusher block 250 which moves the tread may require a small amount of adjusting for certain kinds of stairs and this is accomplished by inserting a threaded bolt 256 in the pivotal member 251 so that block 250 may be slightly adjusted for its engaging position. Plate 255 is secured to vertical connectors 260, 261 which connect with member 262 that in turn connects to vertical member 265 which is secured to cylinder rod 266 of the double acting pusher actuating cylinder 267 mounted on fixed frame plate 268. Connectors 260, 261 are secured to a hollow guide sleeve 270 which slides on a fixed rod 271 having a threaded portion 272 with an adjustable stop nut 273. In operation, pusher block 250 is moved forward by having cylinder 267 actuated to extend its rod 266 so as to advance plate 255 and thereby advance block 250. The limit of forward movement is controlled by appropriate positioning of the stop nut 273. In its most forward position it will be understood that pusher block 250 will be pushing on the underside of the stair against a respective tread while the end portion 210 of the stop mechanism S will be pushing in the opposite direction on an upper surface'of the stair as somewhat schematically illustrated in FIG. 15.

A generalized control diagram is shown in FIG. 2. An electric motor and gear box 215 operates from an AC supply 216 through an on/off switch 217, also shown in FIGS. S and 13, and the supply to motor 215 is further controlled by an electric safety switch 140 which operates through suitable relays and the like, not shown, and which mounts on rail (FIG. 11). In operation motor 215 will only operate when electric safety switch has been engaged by the stair stringer and when operating turns a series of control cams 218, 219, 220 and 221. These cams in turn operate mating cam controlled valves (indicated by CV in FIG. 2) 224, 255, 226 and 227. Valves 224, 225 and 226 are 4-way pneumatic valves and valve 226 is a 3-way pneumatic valve. The pusher mechanism cylinder 267 is provided air from a suitable air supply 230 through appropriate air regulator and oiling means as indicated at 231, FIGS. 5 and 13, but not shown in FIG. 2. For simplification in FIG. 2, only one of the two air supply lines is shown for the respective double acting cylinders. From supply 230 the air is fed through a manual shut off valve 232 (indicated by MV in FIG. 2) and also shown in FIGS. 5 and 13. From valve 232 the air is fed through the cam valve 224 and from valve 224 to pusher cylinder 267. It will of course be understood that cam 218 controls cam valve 224 and accordingly controls the in and out action of the pusher mechanism P.

The stop mechanism S is controlled by cylinder 203 and air in reaching cylinder 203-is fed from supply 230 through the air regulator and oiler previously mentioned, then through the air safety valve 141 which is opened and closed by the presence of the stair stringer the same as in the mentioned safety electric switch 140. From air safety valve 141 the air is fed through a manual shut off valve 234, shown also in FIGS. 5 and 13, then through the cam valve 225 and then to the stop mechanism cylinder 203. From this description it can now be seen that as cam 219 turns which is dependent on electric safety switch 140 being "closed and dependent on air safety valve 141 being open cylinder 203 will be sequentially operated to move the stop mechanism, particularly end portion 210, in and out and in synchronism with other components of the invention apparatus.

Energization of the two cylinders 175 and 176 which move the top nailer bank N-3 down and up and energization of the two cylinders 109 and 110 which move the left nailer bank N-l and the right nailer bank N-2 are all controlled together. In particular, the operating air supply is fed from supply 230 through the mentioned regulator and oiler and then through the air safety valve 141, then through a manual shut off valve 236, then through cam valve 226 and from cam valve 226 to the respective actuating cylinders 109, 110, for side nailer banks N-l and N-2, and cylinders 175 and 176 for the top nailer bank N-3.

The nailing guns are indicated by the label 6" in FIG. 2 and for operation are effectively required to have two sources of air. One source of air is referred to as the supply air and the other as the control air. The supply air effectively remains on constantly and pneumatically energizes the gun but is incapable of firing the gun. The control air is in effect a controlled burst of air which causes the gun to fire. As indicated in FIG. 2, the supply air is connected directly to the guns l32-134 in the left side nailer bank N-l, to the guns 135-137 in the right side nailer bank N-2 and to the guns 150-153 in the top nailer bank N-3. Since the control air is critical both for safety and operation the control air is fed from air supply 230 through the air safety valve 141, through the manual control valve 240, indicated in FIGS. 2, and 13, through the cam control valve 227 and then to all the guns in the respective banks N-l, N-2 and N-3. Thus, firing of the guns is dependent on cam 221 which is dependenton electric safety valve 140 being closed and air safety switch 141 being open. Therefore, the guns actually fire only when the stair is in position and switch 140 and valve 141 are opened by the respective stair stringers being properly positioned on the support rails 50, 55.

To set up the first stair the operator will mark a line on the side of the stringer as a guide to the angle at which the nails are to be driven into the stringer by the automatic nailing equipment. With the power off the machine the stair is then pulled into the machine and the guns in the two side banks N-l, N-2 are adjusted so as to strike this line during the nailing operation. The stair is then clamped between rails 50, 55in the position where the right and left side nailers are aligned with the mentioned pencil marks. Then the indexing mechanism is moved forward until the pusher block 250 engages the tread which corresponds to that particular position of the stair. At this point the indexing mechanism adjusting nut 273 is moved to a position corresponding to the correct stop position for that tread. The stair stop mechanism is also adjusted at this stage by engaging end portion 210 with the stair and adjusting nut 207 (FIG. 12). Before or when adjusting the stair stop the pitch of the guns in the top bank N-3,

is also adjusted by loosening levers 158, 159 and rotating the top gun frame on stub shafts 156, 157 as required. Then the guns in top bank N-3 are sighted against the stair and laterally moved as required to insure that the top gun nails will go into the proper position in the risersQ will, of course, be understood that various operators will adopt their own adjustment procedure and which may differ from that just described.

To summarize, an entire operation will now be described in the light of the foregoing description. After the stairs are assembled it is pushed from the assembly table 35, FIG. 5, forward until the left stringer intercepts the electric safety switch 140 and the right stringer intercepts the pneumatic safety valve 141. In moving the stair forward the pusher block 250 will automatically be pushed down as required to clear the first tread due to the tilting action of support member 251, FIG. 10. At this point the operator stops moving the stair forward and the indexing or pusher mechanism P by now is behind the first tread and block 250 is ready to push against this tread. At this stage the top air guns in bank N-3 are retracted and both the left and right guns in banks N-l, N-2 are retracted. The stair stop cylinder 203 is energized and the end portion 210 moves down and assumes a fixed position before the pusher mechanism P, that is pusher block 250, completes its forward motion. When the stair has been fully advanced by the pusher mechanism P the stair stop S, i.e., end portion 210, will engage a middle portion of the appropriate riser. At this point air will be supplied to the two cylinders 175, 176 which cause the top gun bank N-3 to move down and simultaneously air will be supplied to the left and right cylinders 109, which cause the left and right guns in banks N-l, N-Z'to be pressed in against the sides of the stair. At this point then the pusher mechanism P i.e., block 250, is holding the stair forward, the stop mechanism S. i.e., end portion 210, is pressing 'against the stair and all guns are engaged in their respective positions against the stair. In the next operation the control air is supplied to all guns simultaneously causing them to tire once. The control air lines for the guns effectively geta burst of air. In the type of Paslode gun previously mentioned the control air lines open and close a diaphragm which in turn controls the passage of the main supply of air to the guns reaching the plunger so as to cause one nailing operation.

In the next sequence of operation air is supplied to the opposite sides of the stair stop cylinder 203, the two top gun bank cylinders 175, I76 and the left and right side gun cylinders 109, 110 so as to cause all of these cylinders to simultaneously retract away from the stair and hold a stationary position awaiting the next operation. As soon as the guns are retracted air is supplied to an opposite side of the indexing or pusher cylinder 267 so as to cause the pusher mechanism P, i.e., block 250, to retract to its most rearward position. With one embodiment, in about seven seconds the indexing device, i.e., block 250, moves rearwardly and then again forwardly so as to catch the next successive tread. That is, the entire operation takes seven seconds to complete one complete cycle of nailing and positioning in the embodiment on which the application is based. This sequence continues to repeat until all of the respective treads have been nailed to the respective risers. When the last tread has been nailed "the operator manually moves the stair forward out of the machine. This releases both the electric safety switch and the pneumatic safety valve 141 which automatically shuts the machine down. In the shut down position the indexing mechanism will be retracted, all of the guns will be retracted and the stair stop will be retracted waiting for the next staiLThe just nailed stair will be finished on the receiving. table 34.

What is claimed is:

1. An apparatus for nailing together stringers, treads and risers which have been preassembled into the form of a stair comprising, in combination:

a. an elongated table means including a pair of left and right longitudinal rail members adapted to slidably receive the stringers of a preassembled stair during the nailing of the stringers to the treads;

b. powered indexing means adapted when energized to move from a retracted position to push against a selected portion of the stair to be nailed, to advance another portion of the stair to a nailing station position, to hold the stair from moving rearwardly during nailing, following nailing to retract to the said retracted position without disturbing the forward position of the stair preparatory to repeating said push against another said selected portion to bring another more rearward disposed portion of the stair to the same said nailing station position; automatic side nailer means including a plurality of powered nailing guns adjustably mounted on powered movable carriage means and arranged in right and left banks at said nailing station and adapted when energized for each respective bank and its carriage means to move against a respective stringer and nail through such stringer and into respective tread a plural group of nails laterally aligned and aligned with said tread and upon completion of such nailing to retract away from said stringers preparatory to nailingthe next following tread;

d. automatic top nailer means including a plurality of powered nailing guns adjustably mounted on powered movable carriage means and arranged in a top bank at said nailing station and adapted when energized for said top bank and its carriage means to move against a respective riser and nail through such riser and into the same said respective tread a plural group of nails laterally aligned with said respective tread and upon completion of such nailing to retract away from said riser preparatory to nailing the next following tread; and

. control means adapted to control the energization of said indexing, side nailer and top nailer means in a coordinated operational sequence.

2. In an apparatus as claimed in claim 1, wherein said indexing means, nailing guns, and carriage means are all fluid pressure operated and said control means includes cam control valve means for controlling the energization and firing thereof.

3. In an apparatus as claimed in claim 2, including a stop means which includes a powered movable member mounted adjacent said nailing station and adapted when said indexing means has indexed said stair to said nailing station and is pushing against said selected portion of said stair to assert an opposing force whereby to prevent said stair from moving in the forward direction during said nailing.

4. In an apparatus as claimed in claim 3 wherein said powered movable member comprises a fluid pressure operated member and said control means includes cam control valve means for controlling the energization thereof.

5. In an apparatus as claimed in claim 4 wherein said rail members are laterally adjustable and means in association therewith for simultaneously adjusting the lateral spacing of said rail members.

6. In an apparatus as claimed in claim 5 wherein said indexing means includes a pushing block means adapted to engage the edge of a tread of said stair during indexing and said stop means includes a rod means adapted to engage an opposing riser surface.

7. In an apparatus as claimed in claim 6 wherein the stroke of said indexing means and stop means are adjustable.

8. In an apparatus as claimed in claim 7 wherein said control means includes an electric motor, a set of cams driven by said motor, a set of pneumatic valves controlled by said cams, a safety electric switch operative when engaged by a stringer of said stair and arranged to control the energization of said motor and a safety pneumatic valve operative when engaged by a stringer of said stair and arranged to control the energization of all said guns.

9. In an apparatus as claimed in claim 8 wherein said pushing block means includes a pivotal mount therefor and spring means adapted to urge said pushing block means upwardly.

10. In an apparatus as claimed in claim 9 wherein said side nailer means carriage means includes respective right and left carriage means. and respective right and left supporting frames connecting said respective right and left carriage means to the said respective right and left rail members whereby upon lateral adjustment of said rail members said carriage members and'consequently said right and left banks of nailers are laterally adjusted a corresponding amount.

11. In an apparatus as claimed in claim 10 wherein said stop means powered movable member is mounted on a frame secured to said table means and said top nailer carriage means is mounted on the same said frame and said frame is adjustably tiltably whereby said top nailer bank and said stop means movable member may be simultaneously adjusted in tilt in the same amount.

12. In an apparatus as claimed in claim 11 including slidable mounts for said frame enabling said frame to be moved forwardly and backwardly with respect to said table means thereby enabling the position of said top nailer bank and stop means to be adjusted together and simultaneously. 

1. An apparatus for nailing together stringers, treads and risers which have been preassembled into the form of a stair comprising, in combination: a. an elongated table means including a pair of left and right longitudinal rail members adapted to slidably receive the stringers of a preassembled stair during the nailing of the stringers to the treads; b. powered indexing means adapted when energized to move from a retracted position to push against a selected portion of the stair to be nailed, to advance another portion of the stair to a nailing station position, to hold the stair from moving rearwardly during nailing, following nailing to retract to the said retracted position without disturbing the forward position of the stair preparatory to repeating said push against another said selected portion to bring another more rearward disposed portion of the stair to the same said nailing station position; c. automatic side nailer means including a plurality of powered nailing guns adjustably mounted on powered movable carriage means and arranged in right and left banks at said nailing station and adapted when energized for each respective bank and its carriage means to move against a respective stringer and nail through such stringer and into respective tread a plural group of nails laterally aligned and aligned with said tread and upon completion of such nailing to retract away from said stringers preparatory to nailing the next following tread; d. automatic top nailer means including a plurality of powered nailing guns adjustably mounted on powered movable carriage means and arranged in a top bank at said nailing station and adapted when energized for said top bank and its carriage means to move against a respective riser and nail through such riser and into the same said respective tread a plural group of nails laterally aligned with said respective tread and upon completion of such nailing to retract away from said riser preparatory to nailing the next following tread; and e. control means adapted to control the energization of said indexing, side nailer and top nailer means in a coordinated operational sequence.
 2. In an apparatus as claimed in claim 1, wherein said indexing means, nailing guns, and carriage means are all fluid pressure operated and said control means includes cam control valve means for controlling the energization and firing thereof.
 3. In an apparatus as claimed in claim 2, including a stop means which includes a powered movable member mounted adjacent said nailing station and adapted when said indexing means has indexed said stair to said nailing station and is pushing against said selected portion of said stair to assert an opposing force whereby to prevent said stair from moving in the forward direction during said nailing.
 4. In an apparatus as claimed in claim 3 wherein said powered movable member comprises a fluid pressure operated member and said control means includes cam control valve means for controlling the energization thereof.
 5. In an apparatus as claimed in claim 4 wherein said rail members are laterally adjustable and means in association therewith for simultaneously adjusting the lateral spacing of said rail members.
 6. In an apparatus as claimed in claim 5 wherein said indexing means includes a pushing block means adapted to engage the edge of a tread of said stair during indexing and said stop means includes a rod means adapted to engage an opposing riser surface.
 7. In an apparatus as claimed in claim 6 wherein the stroke of said indexing means and stop means are adjustable.
 8. In an apparatus as claimed in claim 7 wherein said control means includes an electric motor, a set of cams driven by said motor, a set of pneumatic valves controlled by said cams, a safety electric switch operative when engaged by a stringer of said stair and arranged to control the energization of said motor and a safety pneumatic valve operative when engaged by a stringer of said stair and arranged to control the energization of all said guns.
 9. In an apparatus as claimed in claim 8 wherein said pushing block means includes a pivotal mount therefor and spring means adapted to urge said pushing block means uPwardly.
 10. In an apparatus as claimed in claim 9 wherein said side nailer means carriage means includes respective right and left carriage means and respective right and left supporting frames connecting said respective right and left carriage means to the said respective right and left rail members whereby upon lateral adjustment of said rail members said carriage members and consequently said right and left banks of nailers are laterally adjusted a corresponding amount.
 11. In an apparatus as claimed in claim 10 wherein said stop means powered movable member is mounted on a frame secured to said table means and said top nailer carriage means is mounted on the same said frame and said frame is adjustably tiltably whereby said top nailer bank and said stop means movable member may be simultaneously adjusted in tilt in the same amount.
 12. In an apparatus as claimed in claim 11 including slidable mounts for said frame enabling said frame to be moved forwardly and backwardly with respect to said table means thereby enabling the position of said top nailer bank and stop means to be adjusted together and simultaneously. 